1. Technical Field
The present invention relates to a circuit device, a physical quantity detection device, an electronic apparatus, a moving object, and the like.
2. Related Art
A circuit device for detecting a physical quantity based on a detection signal from a physical quantity transducer is already known. For example, in a gyro sensor, a circuit device detects angular velocity or the like based on a detection signal from a vibrating reed which is a physical quantity transducer. The gyro sensor is built into, for example, an electronic apparatus such as a digital camera or a smart phone, or a moving object such as a vehicle or an airplane, and performs hand shake correction, posture control, GPS autonomous navigation, or the like, using a physical quantity such as angular velocity which is detected.
A related art of a circuit device of the gyro sensor is disclosed in, for example, JP-A-2000-221039 and JP-A-2004-239907.
In JP-A-2000-221039 and JP-A-2004-239907, in a case in which arithmetic processing (for example, integration processing) of a physical quantity (for example, angular velocity) which is detected by a vibrating reed is performed, if arithmetic processing such as integration processing is performed on the basis of a clock signal from a clock signal generation circuit with a general configuration which uses only an oscillation circuit such as a CR oscillation circuit, correct arithmetic results cannot be obtained.
As an example in which angular velocity is used as a physical quantity, if an nth angular velocity in a period for integration processing is referred to as ωn and a period corresponding to ωn is referred to as Tn, integration processing is performed by performing multiplication processing of ωn×Tn, and a physical quantity such as an angle is obtained.
However, the frequency of a clock signal which is generated by an oscillation circuit that operates separately from driving of a vibrating reed, can vary depending on process variation or environmental variation (temperature variation, power supply voltage variation, or the like). Hence, if arithmetic processing such as integration processing is performed by using the clock signal, correct arithmetic results cannot be obtained. As an example in which an angle is obtained by performing integration processing of angular velocity, even though an angle of actual rotation of a detection target is, for example, 10 degrees, if a clock frequency varies depending on process variation or environmental variation, problems occur in which an angle which is obtained by integration processing is shifted from the 10 degrees, and a correct angle cannot be obtained.